To date, there is no published study, comparing the effects of lansoprazole and pantoprazole on gastric acid secretion inhibition. The aim of this study, was to compare the effects of these two drugs on 24-h intragastric pH-metry. Twelve healthy volunteers were included in an open, randomized, crossover study. Each subject received lansoprazole 30mg during 7 days followed, after a 14-day wash-out period, by pantoprazole 40 mg for 7 days or vice versa. Intragastric 24-h pH monitoring was performed before the treatment, and then after the first and seventh intake in each treatment period. The decrease in gastric acidity on daytime, night-time and total 24-h periods during both treatments was significantly different from the base value. Significant differences in acid inhibition were found between lansoprazole 30mg and pantoprazole 40 mg during daytime and 24 h after the first intake. After repeated dose regimens, a significant difference was detected between treatment periods but only for pH above 4. After the first dose, the median pH value with lansoprazole was also significantly greater than for pantoprazole. Pantoprazole activity increased significantly from first to seventh intake, in contrast to lansoprazole. Lansoprazole 30 mg was significantly more potent than pantoprazole 40 mg on 24-h pH profiles on the first and seventh days. The antisecretory effect of lansoprazole was maximum after the first intake whereas pantoprazole activity increased significantly between the first and last intake.